[syzbot] [net?] [wireless?] INFO: rcu detected stall in cfg80211_wiphy_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cacc6e22932f tpm: Add a helper for checking hwrng enabled
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b0b5c7a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=3e670757e16affb
dashboard link: https://syzkaller.appspot.com/bug?extid=b904439e05f11f81ac62
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a49fcda80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=136f8679a80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c18b40f6d56d/disk-cacc6e22.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b270ef22b038/vmlinux-cacc6e22.xz
kernel image: https://storage.googleapis.com/syzbot-assets/aae3a8e7d564/bzImage-cacc6e22.xz

The issue was bisected to:

commit c2368b19807affd7621f7c4638cd2e17fec13021
Author: Jiri Pirko <ji...@nvidia.com>
Date: Fri Jul 29 07:10:35 2022 +0000

net: devlink: introduce "unregistering" mark and use it during devlinks iteration

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=123267c3a80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=113267c3a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=163267c3a80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b90443...@syzkaller.appspotmail.com
Fixes: c2368b19807a ("net: devlink: introduce "unregistering" mark and use it during devlinks iteration")

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-....: (10490 ticks this GP) idle=5a24/1/0x4000000000000000 softirq=8393/8393 fqs=5242
rcu: hardirqs softirqs csw/system
rcu: number: 0 0 0
rcu: cputime: 25922 26566 195 ==> 52500(ms)
rcu: (t=10502 jiffies g=5333 q=584 ncpus=2)
CPU: 1 PID: 5054 Comm: kworker/1:4 Not tainted 6.5.0-rc5-syzkaller-00056-gcacc6e22932f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: events cfg80211_wiphy_work
RIP: 0010:taprio_dequeue_tc_priority+0x266/0x4b0 net/sched/sch_taprio.c:798
Code: 10 89 ef 44 89 f6 e8 39 b5 2c f9 44 39 f5 0f 84 40 ff ff ff e8 3b ba 2c f9 49 83 ff 0f 0f 87 e1 01 00 00 48 8b 04 24 0f b6 00 <38> 44 24 36 7c 08 84 c0 0f 85 bf 01 00 00 8b 33 8b 4c 24 30 48 8b
RSP: 0018:ffffc900001e0d60 EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffff88802b8e7394 RCX: 0000000000000100
RDX: ffff888076ac0000 RSI: ffffffff88594e65 RDI: 0000000000000004
RBP: 0000000000000008 R08: 0000000000000004 R09: 0000000000000008
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000010
R13: ffff88807af8ab60 R14: 0000000000000000 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000600 CR3: 0000000022134000 CR4: 0000000000350ee0
Call Trace:
<IRQ>
taprio_dequeue+0x12e/0x5f0 net/sched/sch_taprio.c:868
dequeue_skb net/sched/sch_generic.c:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x1c4/0x19d0 net/sched/sch_generic.c:415
qdisc_run include/net/pkt_sched.h:125 [inline]
qdisc_run include/net/pkt_sched.h:122 [inline]
net_tx_action+0x71e/0xc80 net/core/dev.c:5049
__do_softirq+0x218/0x965 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0xb7/0x120 kernel/softirq.c:644
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1109
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
RIP: 0010:__ieee80211_link_release_channel+0x2/0x450 net/mac80211/chan.c:1778
Code: 89 f7 e8 81 1f 21 f8 e9 44 e0 ff ff 4c 89 f7 e8 74 1f 21 f8 e9 fe fb ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 41 57 <41> 56 41 55 41 54 55 53 48 89 fb e8 3e 15 cd f7 48 89 da 48 b8 00
RSP: 0018:ffffc90003cff768 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888076ac0000 RSI: ffffffff89b909f5 RDI: ffff8880677463a8
RBP: ffff8880677463a8 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888067744c80
R13: ffffc90003cff890 R14: ffff888066980e20 R15: ffff888067746c82
ieee80211_link_use_channel+0x2dd/0x750 net/mac80211/chan.c:1849
__ieee80211_sta_join_ibss+0x5f3/0x17e0 net/mac80211/ibss.c:303
ieee80211_sta_create_ibss+0x206/0x410 net/mac80211/ibss.c:1352
ieee80211_sta_find_ibss net/mac80211/ibss.c:1482 [inline]
ieee80211_ibss_work+0xc19/0x15a0 net/mac80211/ibss.c:1709
ieee80211_iface_work+0xbb8/0xd40 net/mac80211/iface.c:1680
cfg80211_wiphy_work+0x24e/0x330 net/wireless/core.c:435
process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2600
worker_thread+0x687/0x1110 kernel/workqueue.c:2751
kthread+0x33a/0x430 kernel/kthread.c:389
ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
</TASK>


---
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[Hillf Danton]

On Sun, 13 Aug 2023 17:48:47 -0700

> HEAD commit: cacc6e22932f tpm: Add a helper for checking hwrng enabled
> git tree: upstream

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=136f8679a80000

Check if it is a rcu hog for taprio to dequeue.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cacc6e22932f

--- x/net/sched/sch_taprio.c
+++ y/net/sched/sch_taprio.c
@@ -787,6 +787,7 @@ static struct sk_buff *taprio_dequeue_tc
int num_tc = netdev_get_num_tc(dev);
struct sk_buff *skb;
int tc;
+ int loop = 0;

for (tc = num_tc - 1; tc >= 0; tc--) {
int first_txq = q->cur_txq[tc];
@@ -805,6 +806,8 @@ static struct sk_buff *taprio_dequeue_tc

if (skb)
return skb;
+ if (loop++ > 50)
+ return NULL;
} while (q->cur_txq[tc] != first_txq);
}

--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b90443...@syzkaller.appspotmail.com

Tested on:

commit: cacc6e22 tpm: Add a helper for checking hwrng enabled
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10e1bc65a80000

kernel config: https://syzkaller.appspot.com/x/.config?x=3e670757e16affb
dashboard link: https://syzkaller.appspot.com/bug?extid=b904439e05f11f81ac62
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1338569ba80000

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit da71714e359b64bd7aab3bd56ec53f307f058133
Author: Jamal Hadi Salim <j...@mojatatu.com>
Date: Tue Aug 22 10:12:31 2023 +0000

net/sched: fix a qdisc modification with ambiguous command request

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14e978e9680000
start commit: cacc6e22932f tpm: Add a helper for checking hwrng enabled
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=3e670757e16affb
dashboard link: https://syzkaller.appspot.com/bug?extid=b904439e05f11f81ac62

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14a49fcda80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=136f8679a80000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: net/sched: fix a qdisc modification with ambiguous command request

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.